Superheterodyne receiver for very short waves



Aprifi 8, 1952 A. VAN WEEQL SUPERHETERODYNE RECEIVER FOR VERY SHORT WAVES Filed July 20, 1946 LOCAL OSCILLATOR 3g I .F OUTPUT IN V EN TOR. ADELBERI VAN WEL M AGEWZ Patented Apr. 8, 1952 SUPERHETERODYNE RECEIVER FOR VERY SHORT WAVES Adelbert van Weel, Eindhoven, Netherlands, as-

signor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application July 20, 1946, Serial No. 685,200 In the Netherlands July 26, 1943 Section 1, Public Law 690, August 8, 1946 Patent expires July 26, 1963 2 Claims. (Cl. 250-20) Patent application Serial No. 668,538 filed May 9, 1946, now Patent No. 2,505,251 dated April 25, 1950 discloses a superheterodyne receiver for very short waves, in which the local oscillations are supplied in the same phase and the incoming oscillations through a tunable Lecher wire system in push-pull to the mixing tube, and in which the oscillatory system formed by the two Lecher wires jointly with respect to the surroundings has such an electrical length that at the points, where the antenna is connected to the Lecher wire sys-' tem, a potential node appears in regard to the local oscillations.

The expedient referred to in patent application Serial No. 668,538 has for its object to reduce as much as possible the emission of the local oscillations. By connecting the antenna to a potential node in regard to the local oscillations a very slight emission is obtained, it is true, but in some cases the emission is not yet prevented to a sufiicient degree.

The present invention has for its object to provide an improved circuit arrangement, by which the emission is still further reduced.

According to the invention the antenna is connected to the said points of the Lecher wire system through a filter which transmits the incoming oscillations but stops the local oscillations.

The said filter is preferably designed in such a manner that the antenna is connected to the said points of the Lecher wire system through a transmission line to which a side-branch, which is tuned to the incoming oscillations, is connected at an electric distance of a quarter of a wavelength of the local oscillations from the said points, of which side branch the two wires jointly constitute an oscillatory system with respect to the surroundings, which has such an electrical length as to produce a potential node in regard to the local oscillations at the junction to the transmission line.

In order that the invention may be clearly understood and readily carried into effect it will now be explained more fully with reference to the accompanying drawing representing, by way of example, one embodiment thereof.

In the superheterodyne receiver represented in the drawing the oscillations picked up by a dipole antenna I, 2 are supplied to a pair of conductors 3, 4 forming part of a Lecher :wire system which is tuned to the frequency of the incoming oscillations through the intermediary of a shortcircuit bridge 5. The antenna. I, 2 is connected to such points I4, I5 of the Lecher wire system as to secure correct accommodation to the mixing 2 tube. The conductors 3 and 4 are connected to the anodes '6 and I of a double diode 8. The cathode 9 of the tube 8 is connected to earth through a source of potential I 0 supplying the 10- cal oscillations. Consequently the incoming oscillations are supplied in push-pull connection and the local oscillations in the same phase to the mixing tube 8. l The intermediate frequency oscillations can now be taken in push-pull connection.

from the circuit arrangement, for which purpose a resonant circuit tuned to the intermediate fre quency, if required in series with one or more high frequency chokes, may be interposed between the anodes of the diode.

The two Lecher wires 3 and 4 jointly carry, with respect to earth, a voltage having the frequency of the local oscillations, due to which the antenna I, 2 might emit the local oscillations. To prevent this, according to patent application Serial No. 668,538, the Lecher wires 3 and 4 are lengthened by parts II and I2 whose ends are connected through an earthed short-circuit bridge I 3, the said extension being chosen in such a manner that the stationary wave having the frequency of the local oscillations, which appears,

in the wires 3, II and 4, I2 jointly, has a potential node at the end I3 and in addition a potential node at the junctions I4, I5 to the antenna I, 2. Instead of the said extension of the Lecher wire system a concentrated inductance or capacity may be provided between the short-circuit bridge *5 and earth. Under these conditions the emission of the local oscillations by the antenna I, 2 is prevented for the greater part but not entirely.

According to the invention a further suppression of this emission is ensured by interposing a. filter between the antenna I, 2 and points I4, I5, by which filter the incoming oscillations are transmitted but the local oscillations are suppressed. To such end the antenna I, 2 is connected to points I 4, I5 through a transmission line I6, I! to which a side branch 20, 2| is connected at I8, I9. The electrical distance of points I4, I5 from points I8, I9 corresponds with a quarter wavelength of the local oscillations. The side-branch 20, 2| is tuned to the incoming oscillations through a short-circuit bridge 22. Behind this short-circuit bridge the conductors 20 and 2I are lengthened by parts 23, 24 whose ends are connected through an earthed short-circuit bridge 25 and whose length is chosen in such a manner that the oscillatory system formed by the conductors 20, 23 and 2|, 24 jointly has an electrical length of half a wavelength in regard to the local oscillations, so that a potential node in regard to the local oscillations appears at I8, l9. Instead of the extension 23, 24 a concentrated inductance or capacity may be provided between the short-circuit bridge 22 and earth. The said parts I6 to 25 jointly constitute a very effective filter by which the oscillator frequency is practically entirely suppressed.

What I claim is:

l. A circuit arrangement for mixing a first wave and a second wave to produce an intermediate frequency wave, comprising a pair of mixing elements, means to generate said first wave and to apply said first wave to said mixing elements in inphase relationship, a first Lecher system having an open end thereof coupled to said mixing elements in push-pull relationship and having a closed end to produce on said first Lecher system a first voltage node of said first wave at said closed end of said first Lecher-system and a second voltage node of said first wave at a point on said first Lecher system intermediate to said closed end and said mixing elements, first bridge means positioned intermediate to the closed end of said first Lecher-system and said mixing elements to tune said first Lecher-system to the frequency of said second wave, an antenna system to receive said second wave, a transmission line coupled between said antenna system and said point on said first Lecher-system, a second Lecher system having an open end thereof coupled to said transmission line at a point thereon an odd multiple quarter wave length of said first wave from said point on said first Lecher-system and having a closed end to produce a third voltage node of said first wave at said point on said transmission line, and second bridge means to tune said second Lecher system to the frequency of said second Wave.

2. A circuit arrangement for mixing a first wave and a second wave to produce an intermediate frequency wave, comprising a pair of mixing elements each having an anode electrode and having a common cathode, means to generate said first wave coupled between said cathode and 4 ground potential, a first Lecher-system having an open end thereof coupled to said anodes in push-pull relationship and having a closed end coupled to ground to produce on said first Lecher-system a first voltage node of said first wave at said closed end of said first Lecher-system and a second voltage node of said first wave at a point on said first Lecher-system intermediate to said closed end of said first Lecher-system and said anodes, first bridge means positioned intermediate to the closed end of said first Lecher-system and said anodes to tune said first Lecher-system to the frequency of said second wave, an antenna system to receive said second wave, a transmission line coupled between said point on said first Lecher-system and said antenna means, a second Lecher-system having an open end thereof coupled to said transmission line at a point thereon an odd multiple quarter wave length of said first wave from said point on said first Lecher-system and having a closed end to produce a third voltage node of said first wave at said point on said transmission line, and second bridge means to tune said second Lecher-system to the frequency of said second wave.

ADELBERT VAN WEEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 4 1,933,669 Gilman Nov. 7, 1933 1,980,158 Hansell Nov. 6, 1934 2,106,776 Trevor Feb. 1, 1938 2,211,003 Conklin Aug. 13, 1940 2,227,078 Gerhard Dec. 31, 1940 2,238,438 Alford Apr. 15, 1941 2,260,844 Thomas Oct. 28, 1941 2,382,693 Dallenbach Aug. 14, 1945 2,441,452 Strutt May 11, 1948 2,453,078 Posthumus Nov. 2, 1948 2,479,537 Fyler Aug. 16, 1949 

